The present invention relates to a system and method for delivering emulsion explosive compositions (hereafter xe2x80x9cemulsion compositionsxe2x80x9d) into a borehole by means of an oversized diaphragm pump, which provides a relatively constant flow rate for the pumped emulsion composition thereby minimizing flow pulsations during delivery. More specifically, the system and method comprise an oversized diaphragm pump of significantly higher capacity than the intended flow rate of the emulsion composition, in combination with a water injection system that provides a lubricating annular stream of pressurized water between the pumped emulsion composition and the inner surface of a delivery hose for delivering the composition into a borehole. By minimizing flow pulsations, a safe, simple and easy to handle system and method for the delivery of emulsion compositions into boreholes are provided. Moreover, the diaphragm pump operates at a relatively low pressure which also enhances safety.
The emulsion compositions of the present invention comprise water-in-oil emulsions that are used as explosives or blasting agents in mining or construction applications and are well known in the art. See, for example, U.S. Pat. No. 4,931,110. U.S. Pat. No. 5,686,685 (""685) discloses a simple system for the pneumatic delivery of emulsion explosives. After describing prior art methods for pumping emulsion explosives, the ""685 patent discloses a system comprising a pressurized vessel for holding an emulsion explosive under pressure, which then is pneumatically discharged from the vessel and through a water injection system that provides an annular stream of pressurized water around the extruded emulsion explosive. Although this system satisfies safety concerns attendant other prior art pumping systems, which generally require higher pumping pressures and dynamic operations, the pressurized emulsion vessel is a relatively expensive and cumbersome piece of equipment. Further, a pressurized emulsion vessel, being of significant volume, increases the potential safety hazards associated with compressed gas systems.
In contrast, the system and method of the present invention retain the low pressure advantages of the ""685 patent system, but utilize significantly less expensive equipment and particularly do not require an expensive, relatively large volume pressure vessel. Moreover, the flow rate of the emulsion composition in the present invention is surprisingly more constant and reliable during the repeated start-ups and shut-downs involved in borehole loading than that experienced with the ""685 patent system. The oversized diaphragm pump is key to providing this constant flow rate.
The invention comprises an underground or surface delivery system for delivering emulsion compositions into a borehole further comprising:
(a) a bin for holding ail emulsion composition and having an outlet,
(b) an oversized diaphragm pump connected to the bin outlet and to a power source for pumping the emulsion composition from the bin and through an outlet from the pump at a relatively constant flow rate thereby minimizing flow pulsations,
(c) a water injector connected to the pump outlet for forming an annular stream of water around the emulsion composition,
(d) a source of pressurized water for providing water to the water injector,
(e) optionally, means for introducing trace gassing ingredients into the emulsion composition downstream from the diaphragm pump, and preferably upstream of the water injector,
(f) a delivery hose extending from the water injector for delivering the emulsion composition into a borehole, and
(g) optionally, a mixing device at or near the end of the delivery hose for mixing the optional trace gassing ingredients into the emulsion composition.
This delivery system is safe, simple and easy to handle and minimizes flow pulsations.